Something extremely handy for sketching (9)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
thumbnail
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for thumbnail that I've seen before include "This sketch is short and concise like manual appendage" , "small picture" , "Kind of sketch r" , "Digital process" , "Brief description" .)